The present embodiments relate to a local coil for a magnetic resonance tomography (MRT).
Magnetic resonance devices (MRTs) for examining objects or patients using magnetic resonance tomography are known, for example, as disclosed by DE10314215B4.
In MR tomography, images with a high signal-to-noise ratio (SNR) may be recorded using local coils (e.g., coils). The local coils are antenna systems that may be attached directly on (anterior) or below (posterior) the patient. With an MRT measurement, the excited nuclei induce a voltage into the individual antennae of the local coil. The voltage is then amplified with a low-noise preamplier (LNA, preamp) and is forwarded to the receiving electronics via a cable. High field systems (e.g., 1.5 T to 12 T and more) may be used to improve the signal-to-noise ratio even with highly resolved images.
Of importance in many clinical MR applications is the SNR (signal-to-noise ratio) of an image. The SNR may be decisively determined by the local coil (e.g., antenna with active amplifiers) and by the losses in the antenna elements themselves. Very small antennas allow for a very high SNR close to the antenna. Due to the possibility of the accelerated measurement by k-space subscanning (e.g., parallel imaging, SENSE, GRAPPA), there is a great interest in high-channel, very compact antenna arrays. The individual elements of such high channel, compact antenna arrays may have a totally different alignment relative to the transmit field. In addition to the SNR, the simple usability of the local coil is also an important property of the component. During the time used to apply and position the local coil, the MR system may not be used in any other way. A favorable arrangement of local coil elements together with a workflow-optimized mechanical design is key to the simultaneous optimization of SNR and workflow.
Local coils exist in various designs. Local coils may be dedicated to specific body regions (e.g., the head, heart, prostate, knee, ankle, or shoulder joint) of a patient.
Mechanically flexible local coils adapt to the body, and the SNR is improved due to close proximity to the patient. For example, the variability of patient anatomies is very high in the abdomen and thorax area, making a flexible adaptation of the local coil in at least one direction advantageous.
Flexible coils may be manufactured from mechanically flexible antenna supports. Mechanically flexible antenna supports are incorporated in flexible foam materials. Additional areas for electronics may be rigid, but most are so small that sufficient space remains between for the antennae to bend. Anterior coils to image, for example, the heart or abdomen may be attached to a top side of the patient after he/she has laid on the patient couch. The coils may be fixed to the couch by strips or may rest on the couch due to the high dead weight of the coils.
Problems of known local coils may include that the lateral coverage of the patient with local coils may not be optimal due to the subsequent attachment of the coils. The coils may protrude slightly from the surface. A gap may be produced between posterior coil elements (e.g., a spine coil) permanently integrated into a table and anterior coil elements (e.g., see Sp in FIG. 1). Such arrangements may be less than optimal (e.g., for cardiology imaging), since the heart is positioned slightly laterally offset in the body, making lateral coverage important. Fixing the anterior coil to the patient couch with a belt may cause claustrophobic patients to experience anxiety, since he/she is fixed to the patient couch in a certain way (see FIG. 1). Attaching the coil after positioning the patient on the table may be time-consuming for the user and requires additional installation time (see FIG. 2). Once the patient is on the couch, the coil is to be initially fetched (e.g., coil trolley) and placed and aligned on the patient. In the case of overweight patients, the user may potentially have to move around the couch in order to fasten the belts, thereby increasing the expenditure of time for fastening approximately four belts.
The arrangement of the posterior elements and the anterior elements is not rigidly predetermined because posterior and anterior coils are mechanically separated. A fixed element arrangement may be advantageous to the optimization of the antenna arrays with respect to parallel imaging and contribute to the more efficient use of system resources (e.g., number of channels and computing time).